1. Field of the Invention
The present invention relates to a method for simulating well tests on a discrete fractured reservoir model.
2. Description of the Prior Art
Single-phase flow computing tools are currently used. However, these tools are not applied to the real geologic medium in view of the complexity thereof and instead are applied to a homogenized representation, according to the reservoir model called a “double-medium model” described for example by Warren and Root in “The Behavior of Naturally Fractured Reservoirs”, SPE Journal, September 1963. Any elementary volume of the fractured reservoir is thus modelled in the form of a set of identical parallelepipedic blocks limited by an orthogonal system of continuous uniform fractures oriented in the direction of one of the three main directions of flow (model referred to as “sugar box” model). The fluid flow on the reservoir scale occurs through the fractured medium only, and fluid exchanges take place locally between the fractures. The matrix blocks are not applied to the complex medium. This representation, which does not reproduce the complexity of the fracture network in a reservoir, is however effective but at the level of a reservoir mesh whose typical dimensions are 100 m×100 m.
It is however preferable to carry out the flow calculations on the “real” geologic model instead of an equivalent homogeneous model, which affords the double advantage of allowing:                validation of the geologic image of the reservoir provided by the geologist from all the information gathered on the reservoir fracturation (this validation being performed by comparison with the well test data),        reliably testing the sensitivity of the hydraulic behavior of the medium to the uncertainties on the geologic image of the fractured medium.        
A well-known modelling method is finely meshing the fracture network and the matrix while making no approximation concerning fluid exchanges between the two media. It is however difficult to implement because the often complex geometry of the spaces between the fractures makes difficult the meshing of the spaces. In any case, the number of meshes to be processed is often very large. The complexity increases still further with a 3D mesh pattern.
Techniques for modelling fractured porous media are described in French Patents 2,757,947 and 2,757,957 filed by the assignee. The technique of the first patent relates to determination of the equivalent fracture permeability of a fracture network in an underground multilayer medium from a known representation of the network, allowing systematic connection of fractured reservoir characterization models to double-porosity simulators in order to obtain more realistic modelling of a fractured underground geologic structure. The technique of the second patent relates to simplified modelling of a porous heterogeneous geologic medium (such as a reservoir crossed through by an irregular network of fractures for example) in the form of a transposed or equivalent medium so that the transposed medium is equivalent to the original medium, according to a determined type of physical transfer function (known for the transposed medium).